Add multiple custom UIViewControllers to UIPageViewController - ios

Question

I'm trying to add UIPageViewController to my RootViewController in code. I removed storyboard file according to
Xcode 5 without Storyboard and ARC
and adding “regular” ViewController works perfectly. I adoped methods according to UIPageViewControllerDataSource
Also I tried to simplify logic (instead of implementing ModelController from starting PageView project I add showVCWithIndex: method to pick 1 of 3 VC from vcArray and write it to Mutable Array with 1 VC. Hope you can tell me if I was right or wrong about that.
.m
#import "RootPageViewController.h"
#import "ViewController0.h"
#import "ViewController1.h"
#import "ViewController2.h"
#interface RootPageViewController ()
#property (strong, nonatomic) ViewController0 *vController0;
#property (strong, nonatomic) ViewController1 *vController1;
#property (strong, nonatomic) ViewController2 *vController2;
#property (strong, nonatomic) UIPageViewController *pageViewController;
#property (strong, nonatomic) NSArray *vcArray;
#property (strong, nonatomic) NSMutableArray *viewController;
#end
#implementation RootPageViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.pageViewController = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStyleScroll navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:nil];
self.pageViewController.dataSource = self;
_vController0 = [[ViewController0 alloc] init];
_vController1 = [[ViewController1 alloc] init];
_vController2 = [[ViewController2 alloc] init];
NSUInteger index = 0;
NSMutableArray *viewController = [NSMutableArray arrayWithObjects:[self showVCWithIndex:index], nil];
[self.pageViewController setViewControllers:viewController
direction:UIPageViewControllerNavigationDirectionForward
animated:NO
completion:nil];
[self addChildViewController:self.pageViewController];
[self.view addSubview:self.pageViewController.view];
CGRect pageViewRect = self.view.bounds;
self.pageViewController.view.frame = pageViewRect;
[self.pageViewController didMoveToParentViewController:self];
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
viewControllerBeforeViewController:(UIViewController *)viewController
{
NSUInteger index = [self.vcArray indexOfObject:viewController];
if ((index == 0) || (index == NSNotFound)) {
return nil;
}
index--;
return [self showVCWithIndex:index];
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
viewControllerAfterViewController:(UIViewController *)viewController
{
NSUInteger index = [self.vcArray indexOfObject:viewController];
if (index == 2 || index == NSNotFound) {
return nil;
}
index++;
return [self showVCWithIndex:index];
}
- (UIViewController *)showVCWithIndex: (NSUInteger)index
{
self.vcArray = [NSArray arrayWithObjects: _vController0, _vController1, _vController2, nil];
UIViewController *currentVC = [self.vcArray objectAtIndex:index];
return currentVC;
}
#end
EDIT
got the solution (this code works, but I'm not sure if I am 100% right)

Answer 1

When you call...
[self.pageViewController setViewControllers:[vcArray objectAtIndex:0]
direction:UIPageViewControllerNavigationDirectionForward
animated:NO
completion:nil];
... you are setting a nil view controller to the pagination view controller.
[vcArray objectAtIndex:0] points to _vController0 which is, in that moment, nil (you haven't instantiated it yet).
Before set you view controllers into the pagination, you must get it from the storyboard using [self.storyboard instatiateViewControllerWithIdentifier:#"YourViewControllerIdentifier"] or simply calling a alloc init, if you are using Xibs.

Answer 2

When you set the view controllers in your UIPageViewController it has to be an array with only one view controller. The method -setViewControllers:direction:animated:completion: is so misleading. I had the same problem as you when I created a page view controller for the first time.
To allow your page view controller to display other view controllers you return them in the UIPageViewControllerDataSource methods -pageViewController:viewControllerBeforeViewController: and -pageViewController:viewControllerAfterViewController:.